Context should include planetary constants

[ChristopherRabotin]

Context should include planetary constants (these should be not inherited by children nodes because lack of constant definition does not imply that the same constant is applicable in the child's context).

• Convert a set of KPL/TPC files into the ANISE equivalent format
• Convert the KPL/TPC nutation and precession angles into ANISE equivalent format
• Compute the phase angles given an Epoch cf Structures and traits for rotation mathematics ( SO(3) group ) #35
• Lookup of planetary data from the Context provided a NAIF ID if that data is stored as constants (i.e. TPC equivalent)
• Lookup of planetary data from the Context provided the &str name if that data is stored as constants (i.e. TPC equivalent)
• Lookup of planetary data from the Context provided a NAIF ID if that data is stored as a set of interpolated coefficients from BPC
• Lookup of planetary data from the Context provided the &str name if that data is stored as a set of interpolated coefficients from BPC